Firearm receiver and bolt with cooperating guide means



M r h 1969 R. J- CREAMER 3,431,668

FIREARM RECEIVER AND BOLT WITH COOPERATING GUIDE MEANS Filed June 22. 1967 INV ROBERT J CREAMER ATTORNEY FIG -3 ENTOR United States Patent 2 Claims ABSTRACT OF THE DISCLOSURE A firearm of the type wherein a bolt having opposed guide lugs is mounted in a receiver having internal guide grooves. One of the guide grooves is interrupted by an ejection port. Guide means are positioned in the receiver below the interrupted guide groove to mate with guide means on the bolt to properly guide the bolt during movement.

This invention relates generally to firearms. More particularly, this invention relates to a bolt action firearm having a bolt and receiver of particular configuration.

Some bolt action firearms include a tubular receiver having a breech bolt mounted therein for reciprocal movement between a breech open and a breech closed position. The breech bolt is provided with a pair of opposed lug members adjacent its forward face which are contained within grooves in the receiver. Each of the grooves in the receiver comprise upper and lower surfaces upon which the upper and lower surfaces on each of the lugs ride. For right-handed shooters, the bolt is adapted to be locked in the breech closed position by turning the bolt handle clockwise when viewing the firearm from the rearward end toward the front. The receiver has a portion of its length cut away to provide an ejection port which extends from the lower guide surface of the righthand guide groove clockwise circumferentially around the receiver to a point usually over 90 therefrom.

With the above described arrangement, there is no upper guide surface for the right-hand guide lug during movement of the breech bolt past the ejection port. This presents a problem during opening of the breech bolt since the breech bolt must be rotated counterclockwise to unlock it from its closed position and then moved rearwardly. When this is done in a rapid manner, the rotational force tends to be applied to the bolt during the rearward stroke. Once the bolt lugs pass into the area of the ejection port, there is nothing to support the upper surface of the right-hand lug. The only support is provided by virtue of the bottom surface of the left-hand breech lug sliding on the bottom surface of its respective groove. The failure to support both sides of the bolt causes the bolt to slightly cant and causes a binding action to occur between the bottom of the right-hand bolt lug and the bottom guide surface resulting in a rough and uneven movement.

It is therefore an object of this invention to provide an improved bolt and receiver arrangement for a firearm which eliminates the above mentioned problems.

More specificially, it is an object of this invention to provide a bolt and receiver arrangement wherein binding of the bolt in the receiver upon opening of the bolt is eliminated.

Yet another object of this invention is to provide a bolt of the general type having two opposed lugs especially designed for use in a receiver of the type having .an ejection port characterized by smooth action during the opening of the bolt.

These and other objects of the invention will become more apparent by reference to the following description of a preferred embodiment and to the accompanying drawings in which:

FIGURE 1 is a partial sectional view through the receiver portion of a firearm with the bolt, magazine, and firing mechanism omitted for the sake of clarity;

FIGURE 2 is a transverse sectional view of the receiver of FIGURE 1 taken along the lines 2-2 of FIG- URE 1;

FIGURE 3 is a side elevational view of a breech bolt constructed to be used in connection with the receiver shown in FIGURE 1; and

FIGURE 4 is a transverse sectional view of the receiver of FIGURE 1 taken along the lines 44 of FIG- URE 1 with the addition of a bolt member of FIGURE 3 shown in an unlocked position.

Referring to the drawings, and especially to FIGURE 1, a firearm constructed in accordance with the present invention includes a receiver 2 mounted on a stock 4. A barrel member 6 is threadedly attached to the forward end of the receiver 2.

The receiver 2 is generally tubular and includes oppositely disposed, internal guide grooves 8 and 10. Each guide groove 8 and 10 includes an upper guide surface 12 and 14 respectively, and lower guide surfaces 16 and 18 respectively. A portion of the wall of the receiver 2 is cut away to provide an ejection port 20. As can be seen particularly in FIGURE 2, the ejection port 20 extends from a point planar with the bottom guide surface 16 of groove 8 a distance greater than about the wall of the receiver 2, but terminates short of a point lying in a plane coincident with the plane of the upper guide surface 14 of guide groove 10.

As is conventional, the forward portion of the receiver 2 to which the barrel 6 is attached is provided with an enlarged counterbore 22. The base of the counterbore 22 is provided with two tapering portions 24 to urge a bolt forwardly to hold a cartridge securely in the chamber of the barrel 6 when the bolt is rotated into the cocked position. As is also conventional, the receiver comprises. an opening 26 in its bottom surface to which a magazine (not shown) may be attached and through which cartridges may be fed.

In accordance with the present invention, the receiver is provided with an elongated key member 28 which extends from the tapered portion 24 at the base of the counterbore 22 at the forward end of the receiver 2 substantially the entire length of the receiver. As can be seen by FIGURES 2 and 4, the top surface 30 of the keyway is coplanar with the bottom surface 16 of groove 8. Depending upon the type of trigger mechanism used, such key member may be interrupted as at 32 to provide space for various elements of the trigger mechanism (not shown). However, the key 28 should extend the entire distance over which the front portion of the bolt 33 travels from its bolt open to its bolt closed position.

The bolt 33 as shown in FIGURES 3 and 4 includes the conventional, opposed lug members 34 and 36, an elongated body portion 38 and a cocking handle 40. Each of the lug members 34 and 36 include an upper surface 42 and 44 respectively, adapted to be guided by the guide surfaces 12 and 14 respectively of the guide grooves 8 and 10. The bottom surfaces 46 and 48 of the lugs 34 and 36 are adapted to ride on the guide surfaces 16 and 18 respectively, of the guide grooves 8 and 10. The bolt is further provided with an outstanding projec tion 50 immediately below the lug 34. The projection 50 has an upper surface 52 spaced from the bottom surface 46 of lug 34 a distance substantially equal to the thickness of the key 28. The space between surfaces 46 and 52 provides a keyway 54 into which the key 28 extends as shown in FIGURE 4.

In operation, when the bolt is in its fully closed position, the lug members 34 and 36 are positioned immediately forward of the base of the counterbore 22. When the bolt handle 40 is rotated into the position shown in FIGURE 4, which is the unlocked position, and the bolt moved rearwardly, the lugs 34 and 36 are received within the grooves 8 and 10 respectively, and the key 28 received within the keyway 54.

As the front of the lugs 34 and 36 pass the forward edge of the ejector port 20, it will be noted that the bolt 32 is still supported on both sides by virtue of the fact that the upper surface 44 and lower surface 48 is supported on guide surfaces 14 and 18 respectively, and the upper surface 52 defining the keyway '54 is supported by the bottom surface of the keyway 28 and the lower surface 46 of guide lug 34 can ride on surface 16. Thus, it can be seen that as the bolt face clears the ejection port 20, it there is a tendency of the shooter to apply rotational movement to the bolt in a clockwise direction as shown in FIGURE 4, such rotational movement will be opposed by the bottom surface 18 of the guide groove 10 and the bottom surface of the key 28, thereby offering support on both sides of the bolt 32. This eliminates the binding prevalent in systems not incorporating the key and keyway arrangement of the present invention.

What is claimed is:

1. In a firearm, a receiver having first and second oppositely disposed guide grooves therein, each of said guide grooves including an upper planar guide surface and a lower planar guide surface, the upper guide surfaces of each groove being coplanar with each other and the lower guide surface of each of said guide grooves being co-planar with each other, an ejection port in said receiver extending about said receiver from a point coplanar with the lower guide surface of said first guide groove and terminating at a point short of the upper surface of said second guide groove, bolt means mounted in said receiver for movement between a bolt open and a bolt closed position, said bolt means including first and second oppositely disposed guide lugs adjacent the front of said bolt means, each of said guide lugs including upper and lower guide surfaces to be contained between the upper and lower guide surfaces of their respective guide groove, said bolt having a projection below said first guide lug and spaced therefrom to form a key slot having an upper surface defined by the bottom surface of said guide surface of said first guide lug and a lower surface defined by the upper surface of said projection, said receiver having key means defined by the lower guide surface of said first guide groove and a bottom surface extending below said first guide groove, said key slot in said bolt slidably engaging said key means with the upper surface of said key slot being in sliding engagement with the lower guide surface of said first guide groove and the lower surface of said key slot being in engagement with the bottom surface of said key means.

2. The firearm of claim 1 wherein said receiver has a counterbore in its forward end, the bottom surface of said counterbore adapted to be engaged by the rearward faces of said guide lugs in the bolt closed position, said key means extending from the counterbore rearwardly in said receiver to at least the point where the key slot in said bolt will be positioned in the bolt open position.

References Cited UNITED STATES PATENTS 3,030,722 4/1962 Ivy 4216 FOREIGN PATENTS 3/ 1921 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner. 

